Location of online hardness and nitrate monitoring instruments

As part of my manual, I would like to know where within the water treatment plant are the online hardness and nitrate monitoring instruments place. One source stated that the online hardness monitor is placed before the coagulation process, and the online nitrate monitor is placed before the coagulation and after the clear well. Any suggestions?  These two monitoring instruments will then cover majority of the basic instruments found within the water treatment plant that I have discussed in my manual.

Peter